Re: [MMUSIC] [Technical Errata Reported] RFC8864 (7805)

[Christer Holmberg <[e-mail]>]

Hi,

>>>> The issues (AFAIU) is when the offerer sends the *initial* offer,
>>>> with ACTPASS, and creates one or more data channels using SDP. At
>>>> that point the offerer does not yet know whether it will become DTLS
>>>> client or server, but it still has to assign identifiers (odd or even) to 
>>>> the
>>>> data channels.
>>>
>>> Good point. At that point there should be no risk of conflict with
>>> DCEP.
>>> Maybe a revision is needed to deal with that.
>>
>> Yes.
>>
>> And, if DCEP is then later used to create another data channel, it
>> needs to make sure that it does not re-use the same identifier (no matter 
>> if it is
>> odd or even).
>>
>>>> Once the DTLS roles have been determined, the DCEP rules work
>>>> fine also for SDP.
>>>>
>>>> (Personally I have never seen a use-case where both DCEP and SDP
>>>> are used to create and manage data channels.)
>>>
>>> It is hard to envision a use case for it. But as I recall we were trying
>>> to avoid precluding it. One alternative would be for the SDP negotiation 
>>> to
>>> include the choice of either DCEP or SDP for negotiating data channels. 
>>> But
>>> could that be done in a backward compatible way?

The usage of dcmap does indicate such choice in my opinion.

But, again, I cannot guarantee that there are no implementation that use both 
SDP and DCEP within the same session.

>>> If we were able to verify that there is currently no concurrent use in
>>> the wild then perhaps we could amend to say that use of SDP to negotiate
>>> data channels precludes use of DCEP.
>>
>> It is difficult to verify that.
>>
>> But, as discussed above, if we say that in case of ACTPASS the offerer
>> can choose either an odd or even value.
>
> It sounds to me like this is something you'd want to discuss should a -bis
> document ever become a reality, but not confirm the erratum as-is.  Is that
> correct?  If so, then we want "Hold For Document Update" rather than
> "Verified" for this one, correct?

We can discuss whether we should fix this using a -bis or an erratum.

But, the current erratum should not be agreed in its current form.

I think the first thing we need to do is how the solution would look like: the 
easiest solution would be to simply that say:

1)	If one uses SDP one SHOULD/MUST NOT use DCEP
2)	Remove the even/odd requirement when using SDP (at least when using 
ACTPASS)

Regards,

Christer